The top United Nations official in Iraq warned of a "critical humanitarian situation" in the country's west as government forces attempt to regain control of two key cities overrun by Al-Qaeda-linked militants.

U.N envoy to Iraq "Nickolay Mladenov" said today that the humanitarian situation in western Anbar province is likely to worsen as military operations to rout the fighters continue around the cities of Fallujah and Ramadi.

He said stocks of food, water and medicine in Fallujah are beginning to run out, and that more than 5,000 families have fled to neighboring provinces to escape the fighting.